24 cards where the text includes “investigate” and the colors ≤ BR

Ballroom (Ravnica: Clue Edition #12)
Billiard Room (Ravnica: Clue Edition #13)
Carnage Interpreter (Ravnica: Clue Edition #26)
Conservatory (Ravnica: Clue Edition #14)
Dining Room (Ravnica: Clue Edition #15)
Foreboding Steamboat (Murders at Karlov Manor Commander #28)
Foul Play (Innistrad: Midnight Hunt #101)
Hall (Ravnica: Clue Edition #16)
Havengul Laboratory // Havengul Mystery (Universes Within #9)
Havengul Laboratory // Havengul Mystery (Universes Within #9)
Homicide Investigator (Murders at Karlov Manor #86)
Hostile Investigator (The Big Score #10)
Innocent Bystander (Murders at Karlov Manor #133)
Kitchen (Ravnica: Clue Edition #17)
Library (Ravnica: Clue Edition #18)
Lounge (Ravnica: Clue Edition #19)
Magnifying Glass (Murders at Karlov Manor #255)
Persuasive Interrogators (Murders at Karlov Manor #98)
Secret Passage (Ravnica: Clue Edition #20)
Study (Ravnica: Clue Edition #21)
Tamiyo's Journal (Shadows over Innistrad #265)
The Chase Is On (Murders at Karlov Manor #116)
Torch the Witness (Murders at Karlov Manor #146)
Toxin Analysis (Murders at Karlov Manor #107)
Unshakable Tail (Murders at Karlov Manor Commander #29)

It is the moment of discovery, the triumph of the mind, and the end of these results.